Each run of {OnFinishedUnits} can only trigger baseline completion or
top tier completion at most once, so we can pull the call out of the
loop.

R=ahaas@chromium.org

Change-Id: I7eaf42addbbaa9600cb9bf95dce76399be683971
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1889879Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64653}